Quinoxaline: a new directing group for ortho C–H alkenylation / intramolecular ortho C–H cycloamination under open air leading to bioactive polynuclear N-heteroarenes

Abstract

Quinoxaline has been identified as a new directing group for the Pd (or Ru)-catalyzed ortho C–H alkenylation of aniline derivatives and subsequent hypervalent iodine promoted intramolecular ortho C–H cycloamination of the resulting N-arylquinoxalin-2-amine derivatives. This two-step strategy afforded alkenyl substituted benzo[4,5]imidazo[1,2-a]quinoxalines as inhibitors of PDE4. The Pd-catalyzed ortho C–H alkenylation of phenol derivatives was also performed successfully when quinoline was found to be an effective directing group.